Total Electrolyte Concentration Research Articles

Long-term Effect of Sodic Water for Irrigation on Soil Quality and Wheat Yield in Rice-Wheat Cropping System

Increasing scarcity of good quality water in many arid and semi-arid regions necessitates the use of poor quality groundwater for irrigation. Soil degradation resulting from alkali water irrigation has become a serious threat to soil health. In the present study, we conducted an investigation (2021-22) on the physicochemical properties (soil organic carbon, available Na, and available K) of sandy loam soil under a semi-controlled lysimeter. Wheat was grown as an experimental crop, which was irrigated with synthetic alkali waters having similar salts (total electrolyte concentration, TEC = 30 me L−1) and sodium adsorption ratio (SARiw 10 mmol L−1) but varying in residual sodium carbonate (RSC) are being continuously applied since 2004 (20 years). Five types of irrigation water having different levels of residual sodium carbonate comprised. (T1) best available groundwater, (T2) residual sodium carbonate water 1 (RSC- 5 me L–1), (T3) RSC water 2 (RSC 10 me L–1), (T4) RSC water 3 [RSC 10 treated with gypsum (RSC 10 neutralized to RSC 5 me L–1 with gypsum)] and (T5) RSC water 4 [RSC 10 treated with sulphur (RSC 10 neutralized to RSC 5 me L–1 with sulphur)]. Soil samples were collected after harvesting two wheat varieties (KRL 210 and HD 3226). Long-term irrigations with alkali water increased the available Na and K in the soil. Furthermore, soil organic carbon (SOC) decreased significantly with increasing alkalinity of irrigation water. Continuous irrigation with alkali water reduced grain yield of wheat by 31.7% over BAW. Moreover, the addition of gypsum and sulphuric acid has shown some capacity to partially restore soil properties, although not to the level of BAW. The majority of soil parameters under both crop cultivars showed a similar trend. The study's findings led to the conclusion that continuous applications of alkali water drastically degrade soil physicochemical properties. Partial neutralization of alkali water did not allow for the sustained existence of soil physicochemical properties. Consequently, it is recommended that the rate at which amendments are added to alkali water be adjusted to restore the decline in soil physicochemical properties.

A self-driven multifunctional microfluidic sweat analysis system for efficient sweat collection and real-time monitoring

Wearable sweat sensors offer the opportunity for non-invasive and real-time monitoring of metabolite information in sweat, enabling individuals to dynamically monitor their physiology states at the molecular level. However, sweat possesses characteristics such as small volume, volatility, susceptibility to epidermal contamination, and low analyte concentrations, making its reliable collection and detection challenge for wearable sweat sensors. In this work, we develop a self-driven multifunctional microfluidic sweat analysis system (SMMSAS) for efficient sweat collection and detection. The SMMSAS features with a wetting contrast for the sweat, which comprises superhydrophobic inlet, superhydrophilic microchannel enriched with nanofiber, and an absorbent test paper. Such a feature enables the spontaneous sweat transports in the form of dropwise due to the exertion of “Laplace force-capillary force-capillary force” on sweat, thereby facilitating the real-time sweat detection. SMMSAS integrated with the functions of impedance and colorimetry analysis is able to simultaneously record the multiple information in sweat, including sweat volume, sweating rate, total electrolyte concentration, glucose concentration, and pH value, all of which are important to reflect the physiological state of the human body. We also demonstrate the capability of SMMSAS in real-time monitoring the sweating conditions of the human body, which is attributed to its fast responsiveness (∼ 100 ms) for the wide range sweating rate (0.5−15 μL/min) and various total electrolyte concentration (0−80 mM), paving the way for next-generation personalized healthcare.

Effect of Total Electrolyte Concentration and Sodium Adsorption Ratio on Swelling Percentage of Salt Affected Soils in Purna Valley of Maharashtra, India

The present investigation was carried out in the Purna valley of Vidarbha region of Maharashtra to study the effect of total electrolyte concentration and sodium adsorptionratio on swelling percentage of salt affected soils in Purna valley of Maharashtra. The sampling was done in the month of October, 2013. The soil samples were taken from two sites; at the depth of 0-20 cm (surface soil) and 20- 40 cm (sub-surface soil) respectively. For equilibration of soil samples, the synthetic waters were prepared with 4 levels of total electrolyte concentrations (TEC) i.e.10, 20,40,80 meL-1 with three levels of SAR viz., 5, 10 and 15 mmol1/2L-1/2. The increase in swelling percentage was due to the increase in SAR, ESP, levels and also decreases with increasing total electrolyte concentration. The swelling percentage was found to decrease by 27.74 % with increase in TEC levels from 10 to 80meL-1 similarly the swelling percentage was found to increase about 8.94 to 7.81% respectively with increase in SAR levels from 5 to 15 of the equilibrating solution.

Perspiration permeable, textile embeddable microfluidic sweat sensor

Epidermal microfluidic devices are continuously being developed for efficient sweat collection and sweat rate detection. However, most microfluidic designs ignore the use of airtight/adhesive substrate will block the natural perspiration of the covered sweat pores, which will seriously affect normal sweat production and long-term wearable comfort. Herein, we present a Janus textile-embedded microfluidic sensor platform with high breathability and directional sweat permeability for synchronous sweat rate and total electrolyte concentration detection. The device consists of a hollowed-out serpentine microchannel with interdigital electrodes and Janus textile. The dual-mode signal of the sweat rate (0.2–4.0 μL min−1) and total ionic charge concentration (10–200 mmol L−1) can be obtained synchronously by decoupling conductance step signals generated when sweat flows through alternating interdigitated spokes at equal intervals in the microchannel. Meanwhile, the hollowed-out microchannel structure significantly reduces the coverage area of the sensor on the skin, and the Janus textile-embedded device ensures a comfortable skin/device interface (fewer sweat pores are blocked) and improves breathability (503.15 g m−2 d−1) and sweat permeability (directional liquid transportation) during long-term monitoring. This device is washable and reusable, which shows the potential to integrate with clothing and smart textile, and thus facilitate the practicality of wearable sweat sensors for personalized healthcare.

Optimizing Colloidal Stability and Transport of Polysaccharide-Coated Magnetic Nanoparticles for Reservoir Management: Effects of Ion Specificity

In this work we explore the mechanisms of ion-specific stabilization of a polysaccharide-based coating for colloidal nanomaterials used within the oil & gas industry. While nanotechnology has wide prevalence across multiple industries, its utility within this sector is largely undeveloped but has potential applications in areas including (but not limited to) exploration, drilling and production processes. For example, reservoir contrast agents in the form of superparamagnetic nanoparticles could be used to accurately determine the residual oil saturation distribution in a reservoir and thus advise enhanced oil recovery (EOR) efforts. However, deployment of such materials in oil reservoirs proves challenging in cases where high salinity subsurface environments induce nanoparticle aggregation, leading to loss of mobility. Here, we report the synthesis and characterization of dextran-coated superparamagnetic iron oxide nanoparticles (Dex-SPIONs), the colloidal stability of which was evaluated in various brine formulations at elevated temperatures. Initial dynamic light scattering (DLS) measurements reveal a lack of contingency between particle stability and total electrolyte concentration for samples comprised of synthetic seawater and low-salinity brine, the latter fluid of which possesses higher ionic strength yet preserves colloidal integrity to a much greater extent than its seawater counterpart. Further experiments point to a calcium (Ca2+) ion-specific stabilization effect wherein surface complexation of Ca2+ ions to the dextran periphery improves carbohydrate hydration and thus enhances colloidal stability. Ion selective electrode (ISE) measurements provide additional evidence of the Ca2+ - dextran binding interaction, the role of which also factors significantly into mitigation of polysaccharide degradation [as demonstrated through gel permeation chromatography (GPC)]. Finally, we assess the transport of Dex-SPIONs through porous media, including examination of retention properties with respect to variances in ionic composition.

An unconventional vertical fluidic-controlled wearable platform for synchronously detecting sweat rate and electrolyte concentration

Epidermal microfluidic devices with long microchannels have been developed for continuous sweat analysis, which are crucial to assess personal hydration status and underlying health conditions. However, the flow resistance in long channels and the ionic concentration variation significantly affect the accuracy of both the sweat rate and electrolyte concentration measurements. Herein, we present a novel fluidic-controlled wearable platform for synchronously dropwise-detecting the sweat rate and total electrolyte concentration. The unconventional platform consisting of a vertically shortened channel, a pair of embedded electrodes and an absorption layer, is designed to minimize the flow resistance and transform sweat fluidics into uniform micro-droplets for chronological and dropwise detection. Real-time sweat conductance is decoupled from a square-wave-like curve, where the sweat rate and electrolyte concentration can be derived from the interval time and peak value, respectively. Flexible and wearable band devices are demonstrated to show their potential application for hydration status assessment during exercises.

Structural stability and hydraulic characteristics of soils irrigated for two decades with waters having residual alkalinity and its neutralization with gypsum and sulfuric acid

Degradation of soils due to sodification is now widespread in arid and semiarid areas irrigated with groundwater having residual alkalinity. We monitored the changes in soil physical, chemical, and hydraulic characteristics of a sandy loam soil irrigated for the last two decades with two types of alkali waters (AW1, AW2) having similar salts (total electrolyte concentration, TEC=30 me L−1) and sodium adsorption ratio (SARiw 10 mmol L−1) but varying in residual sodium carbonate, RSC (5 me L−1 in AW1 and 10 me L−1 in AW2), and when latter irrigation water (AW2) was ameliorated to neutralize RSC equivalent to 5 me L−1 with either sulfuric acid (AW2 +SA) or gypsum (AW2 +GYP). Deterioration of overall soil quality was evidenced by increased bulk density and penetration resistance, decreased aggregate stability, increased soil pH and sodicity, and decline in accumulation of soil organic carbon, especially with AW2. Exchangeable sodium percentage (ESP) build up ranged between 2.1 and 3.3 times SARiw. The steady infiltration rate (IR) in soil irrigated with good quality water, GQW (Electrical conductivity, ECiw=0.52dSm−1; RSC=1.2 me L−1), was 5.4 mm h−1 (IR-GQW) while it reduced to 2.2, 1.0, 1.7, and 1.8 mm h−1 with AW1, AW2, AW2 +SA, and AW2 +GYP, respectively. The adverse effects of soil sodification exacerbated with rainwater (RW; simulated with deionized water, EC <0.03dSm−1) infiltration, further reducing the IR to 1.1, 0.7, 1.4, and 1.0 mm h−1 for AW1, AW2, AW2 +SA, and AW2 +GYP, respectively. The recovery of IR was only a little (2–11%) when RW was replaced with respective irrigation waters, even when the surface 5 cm was tilled to break soil crusts (ST). This indicates permanent damage to soil structure and water transmission characteristics through the development of sub-soil throttles with moved-in clays. Power functions described the surface soil ESP to control IR (R2 =0.53–0.83 **), and the ESP values for 0.25 IR-GQW were 24.5, 15.8, 17.4, 14.5 and 14.4 for IW (respective irrigation waters), RW, IW-RW, RW-IW, and RW-IW-ST-IW sequences of infiltration events, respectively. There were considerable reductions in post-infiltration water storage in the soil profile, and a slowed down redistribution of infiltrated water were also observed. The neutralization of RSC with either sulfuric acid or gypsum improved the hydro-physical properties; the impact of gypsum being slightly better especially in improving soil stability characteristics.

C-Phycocyanin primed silver nano conjugates: Studies on red blood cell stress resilience mechanism

Green synthesis of metal-encased nutraceutical nano-hybrids has been a target for research over the last few years. In the present investigation, we have reported temperature dependent facile synthesis of silver nanoparticles using FDA approved c phycocyanin (cPC). The cPC conjugated silver nanoparticles (AgcPCNPs) were characterized by TEM, Zeta Potential, UV–vis, XPS, FTIR, and CD Spectroscopy. The temperature optimization studies suggested the synthesis of stable AgcPCNPs at 40 °C while at higher temperature system shows aggregated appearance. Molecular docking studies predicted the exclusive interaction of C, D, I, and J chains of cPC with the surface of AgNPs. Moreover, AgcPCNPs significantly (p < 0.1 %) counteract the toxic nature of AgNPs on red blood cell by measuring parameters like total RBC count, % hemolysis, % hematocrit, coagulation time, pH, electrolyte concentrations and degree of blood cell lipid peroxidation by the anti-oxidation mechanism. Skin fibroblast in vitro cell migration result suggeststhat AgcPCNPs enhanced the degree of cell movement towards the wound area. Data obtained collectively demonstrate that AgcPCNPs can be a better agent in the dermal wound healing with reduced toxicity with the bi-phasic advantage of cPC as a wound healer and Ag nano-metal as an anti-bacterial agent.

Characterization of electrolyte content in urine samples through a differential microfluidic sensor based on dumbbell-shaped defected ground structures

AbstractIn this paper, a differential microfluidic sensor and comparator based on a pair of microstrip lines loaded with dumbbell-shaped defected ground structure resonators is applied to the characterization of electrolyte concentration in samples of horse urine. Since variations in the total electrolyte content in urine may be indicative of certain pathologies, the interest is to use the device as a comparator, in order to determine changes in the electrolyte concentration as compared to a reference level. To validate the approach, we have made differential measurements of a set of urine samples with different electrolyte concentrations (which have been previously obtained by means of electrochemical methods). The obtained results correlate with the nominal electrolyte concentrations of the samples, thereby pointing out the potential of the approach as a low-cost pre-screening method (or complementary diagnosis system) to detect potential pathologies or diseases in horses and other animals.

Correlation of quantitative conductivity mapping and total tissue sodium concentration at 3T/4T.

To investigate the correlation between electrical conductivity and sodium concentration, both measured in vivo, in the human brain. Conductivity measurements were performed on samples with different sodium (Na+ ) and agarose concentrations using a dielectric probe, and the correlation between conductivity and Na+ content was evaluated. Subsequently, brain conductivity and total Na+ content maps were measured in 8 healthy subjects using phase-based MREPT and sodium MRI, respectively. After co-registration and spatial normalization to the 1 mm 152 MNI brain atlas, the relationship between conductivity and tissue sodium concentration (TSC) was examined within different brain regions. The conductivities of agarose gels increased linearly with NaCl concentration, while remaining almost independent of agarose content. When measured in healthy subjects, conductivities showed positive correlation with total tissue sodium concentration (R = 0.39, P < 0.005). The same trend was found in gray matter (R = 0.36, P < 0.005) and in white matter (R = 0.28, P < 0.05). Tissue conductivity shows a positive correlation with total sodium concentration. Conductivity might serve as a novel technique to visualize the total tissue electrolyte concentration, although refinements in the consideration of e.g., tissue water content, would be necessary to improve the quantitative value.

Split Ring Resonator-Based Microwave Fluidic Sensors for Electrolyte Concentration Measurements

A differential microwave sensor, based on a pair of uncoupled microstrip lines each one loaded with a split ring resonator (SRR), is applied to the measurement of electrolyte concentration in deionized (DI) water. For that purpose, fluidic channels are added on top of the SRR gaps, the most sensitive parts of the structure. The operating principle is based on the measurement of the cross-mode insertion loss, highly sensitive to small asymmetries caused by differences between the reference liquid and the liquid under test (LUT). In this paper, the reference liquid is pure DI water (the solvent), whereas the solution, DI water with electrolyte content, is injected to the LUT channel. The proposed sensor is able to detect electrolyte concentrations as small as 0.25 g/L, with maximum sensitivity of 0.033 (g/L)–1. The sensor is validated by measuring the concentration of three types of electrolytes, i.e., NaCl, KCl, and CaCl2. Finally, the sensor is applied to monitor variations of total electrolyte concentration in urine samples.

A pH‐Based Pedotransfer Function for Scaling Saturated Hydraulic Conductivity Reduction: Improved Estimation of Hydraulic Dynamics in HYDRUS

Core Ideas Soil‐specific pedotransfer functions can be incorporated into the HYDRUS model. Electrolyte concentration reduces the adverse effect of pH and Na on soil structural stability. Clay content is important in governing soil hydraulic reduction dynamics due to pH. Hydraulic conductivity is a key soil property governing agricultural production and is thus an important parameter in hydrologic modeling. The pH scaling factor for saturated hydraulic conductivity (Ks) reduction in the HYDRUS model was reviewed and evaluated for its ability to simulate Ks reduction. A limitation of the model is the generalization of Ks reduction at various levels of electrolyte concentration for different soil types, i.e., it is not soil specific. In this study, a new generalized linear regression model was developed to estimate Ks reduction for a larger set of Australian soils compared with three American soils. A nonlinear pedotransfer function was also produced, using the Levenberg–Marquardt optimization algorithm, by considering the pH and electrolyte concentration of the applied solution as well as the soil clay content. This approach improved the estimation of the pH scaling factor relating to Ks reduction for individual soils. The functions were based on Ks reduction in nine contrasting Australian soils using two sets of treatment solutions with Na adsorption ratios of 20 and 40; total electrolyte concentrations of 8, 15, 25, 50, 100, 250, and 500 mmolc L−1; and pH values of 6, 7, 8, and 9. A comparison of the experimental data and model outputs indicates that the models performed objectively well and successfully described the Ks reduction due to the pH. Further, a nonlinear function provided greater accuracy than the generalized function for the individual soils of Australia and California. This indicates that the nonlinear model provides an improved estimation of the pH scaling factor for Ks reduction in specific soils in the HYDRUS model and should therefore be considered in future HYDRUS developments and applications.

Correlation of electric conductivity values with the dairy milk quality

&lt;p class="abstrak2"&gt;Milk, as the prime source of food for mammals, has an electrolyte to replace the loss of body fluid caused by activity or metabolism process. The total electrolyte concentration can be measured based on conductivity value from the nutritional content. Therefore, the parameter of the quality of milk with conductivity value can be a benchmark for quality and selling value of milk, making it simpler to be implemented in the field. The aim of this research is to analyze the relation between electric conductivity (EC) with the content value of cow milk. The milk was taken from 10-30 cows from a farm in Lembang (district of West Bandung), Pengalengan (district of Bandung), Tasikmalaya, Sumedang, Subang, Sukabumi and Bogor of West Java Province. The milk was put in 50 ml of sterile falcon. The Probe EC count-meter CT-3031 was used to measure EC while the quality of milk was measured by Probe MilkoScan&lt;sup&gt;TM&lt;/sup&gt;FT 120 (Foss). The milk quality is reflected by protein content, Fat, Total Solid (TS), Solid Non-fat (SNF), Lactose, Density, Acidity and Freeze Point Deviation (FPD). The results of this study show that the EC value in the milk gives a very real positive effect (p=&amp;lt;0.01) to Total Solid (TS), Solid Non-fat (SNF), Lactose, and Freeze Point Deviation (FPD). The value of EC also significantly affect (p=&amp;lt;0.05) the value of density in milk. Therefore, the value of EC can be used to predict the quality value of milk.&lt;/p&gt;

Extracellular Total Electrolyte Concentration Imaging for Electrical Brain Stimulation (EBS)

Techniques for electrical brain stimulation (EBS), in which weak electrical stimulation is applied to the brain, have been extensively studied in various therapeutic brain functional applications. The extracellular fluid in the brain is a complex electrolyte that is composed of different types of ions, such as sodium (Na+), potassium (K+), and calcium (Ca+). Abnormal levels of electrolytes can cause a variety of pathological disorders. In this paper, we present a novel technique to visualize the total electrolyte concentration in the extracellular compartment of biological tissues. The electrical conductivity of biological tissues can be expressed as a product of the concentration and the mobility of the ions. Magnetic resonance electrical impedance tomography (MREIT) investigates the electrical properties in a region of interest (ROI) at low frequencies (below 1 kHz) by injecting currents into the brain region. Combining with diffusion tensor MRI (DT-MRI), we analyze the relation between the concentration of ions and the electrical properties extracted from the magnetic flux density measurements using the MREIT technique. By measuring the magnetic flux density induced by EBS, we propose a fast non-iterative technique to visualize the total extracellular electrolyte concentration (EEC), which is a fundamental component of the conductivity. The proposed technique directly recovers the total EEC distribution associated with the water transport mobility tensor.

Adsorption of anionic and cationic dyes on biochars, produced by hydrothermal carbonization of waste biomass: effect of surface functionalization and ionic strength

In this work, surface-functionalization agents and various salts as auxiliaries were used to improve the adsorption capacity of biochars produced via hydrothermal carbonization of glucose, cellulose, and hazelnut shell. The effect of surface functionalization with different acids and bases as well as neutral salts on the adsorption of methylene blue and methyl orange was investigated using Boehm titration, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy techniques. Surface functionalization of biochars leads to an increase in the number of oxygen-containing functional groups on the surface, thus increasing the adsorption capacity. To probe the influence of ionic strength on the adsorption process, three auxiliaries, namely potassium chloride, cetyltrimethylammonium bromide, and sodium bicarbonate, were examined. The increase in total electrolyte concentration signicantly affected the pH of the solution and as a result electrostatic interactions between dyes and biochars. Dye adsorption capacities reached 234.57 mg/g for methylene blue and 306.13 mg/g for methyl orange in the presence of cellulose-based and NaOH-functionalized biochar and glucose-based H2SO4-functionalized biochar, respectively.

Cooperative sorption of weak and strong electrolytes in microporous adsorbents

Sorption of pure electrolytes and binary electrolyte mixtures in non-ionic microporous adsorbents was studied in batch and fixed-bed systems. Hypercrosslinked polystyrene (HCPS) and densely crosslinked dextran gel (G10) were used as adsorbents and the studied model systems were HCl/CaCl2/HCPS at 25 °C and Na2-tartrate/NaOH/G10 at 50 °C. The results were explained in terms of cooperative sorption and the experimental data were correlated using a generalized Donnan equilibrium model together with Pitzer model for evaluation of the ion-ion and ion-adsorbent interactions. Moreover, a model was included for partial ion dehydration at high concentrations.Non-linear sorption observed at very low and high concentrations of pure electrolytes was explained by electrostatic exclusion and partial ion dehydration. In binary mixtures, a more complex behavior was observed because of cooperativity and good separation of the electrolyte mixtures was obtained in the fixed-bed experiments involving pulse feed and elution with pure water. In the HCl/CaCl2/HCPS system, selective uptake of HCl was enhanced by increasing the total electrolyte concentration. This trend can be explained by taking into account both size exclusion of CaCl2 and the non-ideal behavior of the electrolyte mixture. Separation of Na2-tartrate and NaOH was dominated by size exclusion of the tartrate anion and well-defined separation is possible even at very high column loading. Moreover, the observed splitting of Na2-tartrate to NaH-tartrate and NaOH can be explained on the basis of cooperativity. The results suggest that the proposed model applies equally well to materials having rigid microporous structure and to densely cross-linked gels.

Integration of ion-exchange and nanofiltration processes for recovering Cr(III) salts from synthetic tannery wastewater

This study aims to investigate the possibility of integrating both ion-exchange (IX) and nanofiltration (NF) processes for the recovery of Cr(III) salts from a synthetic solution prepared with concentrations of Cr(III), and Cl− in the range of industrial effluents of tanneries. Ion exchange should be used as a pre-treatment for uptaking Cl− ions from the effluent, and thereafter the treated solution is fed to an NF unit to recover chromium sulphate salt for reuse in the tanning bath. The strong anionic resin Diaion PA316 was selected for evaluating chloride–sulphate ion-exchange equilibrium, with respect to mass of resin, NaCl concentration, temperature and ratio . It was observed that the separation factor, , depends on the total electrolyte concentration and the ratio plays a role as well. Moreover, it was determined that the resin prefers sulphate over chloride since is less than 1. The performance of the NF process is dependent on and the rejection of Cr(III) may decrease from 90% to 70% as the ratio increases from 0.5 to 2. Regarding the integration of both IX and NF, the feed solution after treatement with the resin was fed to NF where the ratio of led to the best operating conditions for this process (90% of Cr(III) rejection and up to 77% for ions). This strategy may be considered as a sustainable approach since it permits to obtain a solution enriched in Cr(III) salt for reuse in the tanning process, thus contributing to environmental protection.

Impact of Varying Ca/Mg Waters on Ionic Balance, Dispersion, and Clay Flocculation of Salt-Affected Soils

Inceptisols and Vertisols are two dominant soil orders that support major agricultural production in India. These soils often exist in semi-arid and arid regions. Low precipitation and high evaporation demand leads to salt accumulation in these areas. The problem of salt accumulation is further compounded by the presence of saline/alkaline groundwaters. We evaluated the effect of modified Ca/Mg waters on ionic composition, dispersion, and clay flocculation of sodic Inceptisols, saline-sodic Inceptisols, and normal Vertisols from different parts of India. A completely randomized factorial design with three replications of individual soils were sequentially leached with five pore volumes of deionized, saline water of 60 and 120 me L−1 total electrolyte concentration (TEC) at a fixed SAR of 5.0 mmol1/2 L−1/2 and Ca:Mg ratio of 2:1, 1:1 and 1:2. Application of saline waters decreased pH and increased EC of the soil leachates after leaching five pore volumes of three Ca/Mg ratios of 60 and 120 me L−1 solutions in sodic Inceptisols and normal Vertisols. In saline-sodic Inceptisols, application of saline waters decreased both pH and electrical conductivity (EC) of the soil leachates. Preferential Ca2+ holding in soil was only noticed in sodic Inceptisols when leaching process was performed with independent saline waters, but Mg2+ has a tendency to hold in soil upon application of independent saline waters for all soils except sodic Inceptisols. Periodic application of deionized water could increase soil dispersion and decreased flocculation of clay particles. Mg2+ ion had less flocculating vis-à-vis high-dispersion effect on soil clays than the Ca2+ ion.

Unusual concentration dependence of ion-exchange membrane conductivity in ampholyte-containing solutions: Effect of ampholyte nature

Electric conductivity of homogeneous cation-exchange (CMX) and anion-exchange (AMX, AX) membranes in the salt solutions of some organic (lysine hydrogen chloride and potassium hydrogen tartrate (KHT)) and inorganic (sodium dihydrogen phosphate) ampholytes was measured as a function of their concentration. In all cases, an increase in membrane conductivity with diluting external solution was observed at concentrations <0.04molL–1. This trend is not observed in the presence of strong electrolytes, such as NaCl. The effect is explained by a shift in ionic equilibriums caused by decreasing external concentration: increasing Donnan exclusion of H+ ions from an anion-exchange membrane (AEM) as co-ions and increasing fraction of OH− ions in the external solution when it is diluted under a constant pH. This leads to an increase in pH of the internal charged solution in the membrane gel phase and transformation of a part of singly charged ampholyte anions (e.g. H2PO4−) into doubly charged ones (HPO42−). The conductivity increases when one doubly charged counterion replaces two singly charged ones. The mathematical simulation of membrane conductivity concentration dependence provides a good accordance with experimental data. The effect was also simulated by measuring and calculating the conductivity of mixed KHT−K2T external solutions as a function of the equivalent fraction of the tartrate ion (T2−) under condition that the total equivalent electrolyte concentration was maintained constant. The shape of the conductivity vs. concentration curve strongly depends on the ampholyte nature, namely, on the (pK2−pK1)/2 value.

Influence of Water Quality on Exchange Phase-Solution Phase Behavior of Texturally Different Salt-affected Soils

The influence of total electrolyte concentration (TEC) and sodium adsorption ratio (SAR) of water on ESR-SAR relationships of normal clay loam, saline silty loam and calcareous sodic loam soils was studied in a laboratory experiment. Twelve solutions, encompassing three TEC levels viz., 25, 50, and 100 me L−1 and four SAR levels viz., 5, 10, 20 and 30 mmol1/2 L−1/2 were prepared to equilibrate the soil samples using pure chloride salts of calcium, magnesium and sodium at Ca: Mg = 2: 1. The SAR of equilibrium solution decreased as compared to the equilibrating solution and more so in waters of low salt concentration and low SAR. At all electrolyte concentration, SAR values were not attained to the equilibrium solution because of addition of Ca and Mg from mineral dissolution or supply of Ca and Mg from exchange sites. At higher TEC levels, considerable increase in exchangeable sodium percentage (ESP) was observed when it was correlated for anion exclusion and more so in calcareous sodic loam followed by saline silty loam and normal clay loam soils. Irrespective of TEC, the exchangeable sodium in all the soils increased by 2.1 to 3.8-fold and irrespective of SAR, it increased by about 1.1 to 2.1-fold, respectively. So, there is a positive interaction of TEC and SAR in sodification of soils. A positive interaction of TEC and SAR influenced the ESP build-up and CEC and silt + clay content played a major role in the visual disparity in sodification of these soils. Gapon's selectivity coefficient values were perceptible in the order of calcareous sodic loam > saline silt loam > normal clay loam. This indicates the preference of normal clay loam soils for Ca2+ + Mg2+ than that of Na+ on the exchange complex, whereas loam soil exhibited high affinity for sodium. Regression coefficient of ESR-SAR relationships was maximum for sodic loam followed by saline silty loam and normal clay loam soil. The exchange equilibrium was strongly affected by TEC of the solution phase. Variation in soil pH was gradual with respect to TEC and SAR of equilibrating solution and a sharp change was observed. At a fixed TEC, critical ESP values were observed calcareous sodic loam followed by saline silt loam and normal clay loam. On the other hand, SAReq needed for critical ESP built-up was in the order of calcareous sodic loam > saline silt loam > normal clay loam. This may be because of dissolution of calcium bearing minerals in calcareous sodic loam; and wash out of calcium and magnesium from the exchange sites for saline silt loam soil.